public class test05 {
    public ListNode removeNthFromEnd(ListNode head, int n) {
        ListNode dummy = new ListNode(-1,head);
        ListNode slow = dummy;
        ListNode fast = dummy;
        for(int i = 0;i<=n;i++){
            fast = fast.next;
        }
        while(fast!=null){
            slow = slow.next;
            fast = fast.next;
        }
        slow.next = slow.next.next;
        return dummy.next;
    }
}
